Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$202.70	11.264%	$225.5321	$225.53	$225.55	$225.50
Purchase #2	$7.58	13.468%	$8.6009	$8.60	$8.60	$8.60
Purchase #3	$90.29	9.725%	$99.0707	$99.07	$99.05	$99.10
Purchase #4	$106.83	4.159%	$111.2731	$111.27	$111.25	$111.30
Purchase #5	$167.46	13.822%	$190.6063	$190.61	$190.60	$190.60
Purchase #6	$126.67	3.548%	$131.1643	$131.16	$131.15	$131.20
Purchase #7	$137.61	6.700%	$146.8299	$146.83	$146.85	$146.80
7 purchase totals =	$839.14		$913.0773	$913.07	$913.05	$913.10